In connection with navigation or route planning, the term “points of interest”, or POIs in short, refers to locations that are of particular interest due to their services, leisure offerings or tourist attractions. Examples for POIs are filling stations, pharmacies, cash dispensers, vehicle repair shops, accommodations, museums, cinemas or other tourist attractions. Modern navigation devices or route planners indicate POIs along a route to be travelled using different multimedia channels and multimedia formats. For instance, POIs may be output in form of visual symbols, sorted POI lists, voice output and so on.
Navigation devices may be configured to provide a continuous POI search along a route to be travelled. The POI search is in this case based on search areas or search corridors of predetermined sizes. One problem associated with the use of search areas of fixed size is that the number of found POIs may vary considerably from search to search depending on the POI distribution along the route. For instance, POI searches along routes going through urban areas may result in large numbers of found POIs, whereas POI searches performed along routes or route portions involving highways or interconnecting roads between towns or cities may only reveal a few POIs.
Further, POI searches in areas of high POI density require a lot of processing resources and may unnecessarily increase the search time. In order to save processing resources and in order to further increase the search performance, search algorithms may be provided with an exit condition so that the search can automatically be aborted. Such an exit condition may constitute the exceeding of a predetermined threshold value for the found number of POI hits. However, depending on the search algorithm, the set of POIs found before aborting the POI search may not be optimal with regard to distance to the route or distance to a user position. Thus, POI search results and POI search performance may strongly depend from route to route.
In addition, when a route is used for navigation, a POI search can be repeated regularly with different sets of results (due to POIs that have already been passed disappearing from the search result, or due to other POIs appearing in the search result that were previously not found because of an exit condition, or due to the route partially or completely changing because of traffic, user deviation from the original route or user input). Due to the local character of POI distributions, the aforementioned problems are likely to reoccur on subsequent repetitions of the search if performed from a position geographically close to the original search.